Although slightly smaller than gigantic relatives like Giganotosaurus, Acrocanthosaurus was still among the largest theropods ever to exist. The longest known individual measured 11.5 meters (38 ft) from snout to tail tip and weighed an estimated 6,177 kilograms (13,618 lb).[1] Its skull alone was nearly 1.3 meters (4.3 ft) in length.[2]

The skull of Acrocanthosaurus, like most other allosauroids, was long, low and narrow. The weight-reducing opening in front of the eye socket (antorbital fenestra) was quite large, more than a quarter of the length of the skull and two-thirds of its height. The outside surface of the maxilla (upper jaw bone) and the upper surface of the nasal bone on the roof of the snout were not nearly as rough-textured as those of Giganotosaurus or Carcharodontosaurus. Long, low ridges arose from the nasal bones, running along each side of the snout from the nostril back to the eye, where they continued onto the lacrimal bones.[2] This is a characteristic feature of all